The present invention relates to electromagnetic transducers, which may for example be employed in thin film inductive write heads of the type formed on the trailing ends of air bearing sliders used in magnetic recording disk drives.
An inductive transducer used for writing and/or reading magnetic information on storage media, such as a disk or tape, typically includes electrically conductive coil windings encircled by a magnetic core. The magnetic core has leading and trailing pole layers. The pole layers have pole tip surfaces adjacent to the recording media. The magnetic core is interrupted by a submicron nonmagnetic gap disposed between the pole tip surfaces to divert magnetic flux to the media during writing. To write to the media, electric current is flowed through the coil, which produces magnetic flux in the core encircling the coil windings, the magnetic flux fringing across the nonmagnetic gap adjacent to the media so as to write bits of magnetic field information in tracks on the recording media.
The first or leading pole layer is typically substantially flat, whereas the second or trailing pole layer is typically curved because a part of the second pole layer is formed over the coil windings and insulation disposed between the pole layers, while another part nearly adjoins the first pole layer adjacent the gap. The second pole layer may also diverge from a flat plane by curving to meet the first pole layer in a region distal to the media-facing surface, sometimes termed the back gap region, although a nonmagnetic gap in the core does not usually exist at this location.
Thousands of essentially identical inductive transducer heads are formed in a plurality of adjoining solid layers on a wafer substrate. After the layers have been formed on the wafer disk, the disk is cut into bars with a diamond blade, each bar containing many transducers. The sides of the bars, which have a plurality of layers exposed, are lapped to form smooth surfaces for facing recording media. The smooth media-facing surface is typically relieved by etching to improve the interaction of the media-facing surface with the media surface. A coating may be formed on the media-facing surface to protect the reading sensor of the read/write inductive transducer.
An example of a prior art inductive transducer head 20 is shown in FIG. 1A, which depicts portions of the electromagnetic head. The electromagnetic head 20 has been formed in a plurality of adjoining solid layers on a wafer substrate. One of the layers is a trailing pole layer 22 that has been formed over an electrically conductive coil layer with coil sections 24. A protective coating layer 26 forms a media-facing surface 28. The trailing pole layer 22 meets the protective coating layer 26 at a trailing pole tip surface 30. As illustrated, the trailing pole layer 22 has sides 32 that are substantially parallel to each other near the trailing pole tip surface 30. A point at which the parallel sides 32 meet flared sides 36 is often termed a flare point 34.
The width of the pole tip surface 30, which corresponds to the track width, may be decreased to allow more tracks to be written on the recording media. As track width is decreased, however, it becomes more difficult to transmit high-intensity magnetic flux through the pole tip surface. A standard technique for increasing the strength of the magnetic field at the pole tip surface has been to increase the magnetic moment of the material near both the pole tip surface and the recording gap. One way to accomplish this is to form a pedestal of material having a high magnetic moment between a pole layer and the recording gap, increasing the magnetic field at the edge of the pole tip surface adjoining the gap.
As noted above, the trailing pole layer and/or pedestal may have a flared or tapered width near the region around the pole tip surface in which the sides are parallel. Various geometries of tapered pole layers near the pole tip surface have been used, such as the geometries depicted in FIGS. 1B, 1C and 1D. In the cases of the tapered pole layers shown in FIGS. 1B, 1C and 1D, the sides 32 immediately adjacent to the pole tip surface 30 are parallel. The parallel sides 32 of the pole layer near the media-facing surface allow tolerance in the depth of lapping without affecting the track width.
U.S. Pat. No. 6,122,144 to Chang et al. states that it is possible to provide a tapered trailing pole layer that is much wider at an air bearing surface than the leading pole layer without the trailing pole layer broadening the track written to the media. Chang et al. also state that this tapering somehow solves a problem of off track writing by corners of the trailing pole tip.